Smoke and Illumination ammunition

[Blackcloud6]

4th Ed rules say:

Limited Ammunition: Each side in a scenario has a number of turns of smoke equal to 10 percent of the turns in the game, with fractions rounded up. So a 12-turn game allows for two rounds of smoke/illumination, while a 36-turn game would allow four turns. To track usage, place either a Smoke or Illumination marker under the firing unit to indicate one usage, or note off-board artillery's usage on a piece of paper.


This rule uses both "rounds of: and "turns of."  So what does this mean?  if it is a 16 turn scenario then does the side get to fire Illumination only twice, or get to fire illumination on two turns by as many units that can fire it?